Wiegand wire arrangement and method for the production thereof

ABSTRACT

The invention relates to a Wiegand wire arrangement, with a Wiegand wire section, a winding device that defines an inner coil in which the Wiegand wire section is enclosed, and a coil carrier, which is designed as a tubular structure extending between the Wiegand wire section and the inner coil of the winding device inside the inner core, whereby the coil carrier is made of a metallic material.

FIELD OF THE INVENTION

The invention relates to a Wiegand wire arrangement such as is used, forexample, as an electrical voltage source for autonomous absolutesensors.

Wiegand wire arrangements that form an integral part of revolutioncounters are known from DE 102 59 223 B3 and EP 2 221 587 A2.

In a so-called Wiegand module, a coil is wound around the pulse orWiegand wires (see also literature “Wiegand wire: New material formagnetic-based devices”, Electronics, Jul. 10, 1975), which delivers avoltage pulse when the wire is activated by an external magnetic field,which powers, for example, an electronic counting system. The tighterthe coil is wound around the wire, the greater the magnetic coupling.Windings close to a pulse or Wiegand wire generate a greater EMF thanthose further from the wire. Furthermore, with an equal number ofwindings and an equal wire thickness, the internal resistance of thecoil and the associated unavoidable losses are reduced. Nevertheless, itis not recommended to wind the coil directly onto the pulse or Wiegandwire, as this then poses the risk that the functioning of the wire,which is based on magnetostriction, is no longer guaranteed, or is atleast impaired, as a result of the forces occurring.

OBJECT OF THE INVENTION

The primary object of the invention is to produce a robust Wiegand wirearrangement that is advantageously feasible from a production point ofview, whereby the inner coil is close to the pulse or Wiegand wire.

Solution According to the Invention

According to a first aspect of the present invention, theabove-mentioned object is achieved by means of a Wiegand wirearrangement, containing:

-   -   a Wiegand wire section,    -   a winding device that defines an inner coil in which the Wiegand        wire section is enclosed, and    -   a coil carrier, which is designed as a tubular structure        extending between the Wiegand wire section and the inner coil of        the winding device inside the inner core, whereby    -   the coil carrier is made of a metallic material.

In this way, it is possible to produce a Wiegand wire arrangement in anadvantageous manner, whereby the winding device can be attached to ainexpensively produced and mechanically resistant section of tube.

According to the invention, the coil carrier is produced as anon-magnetic or, if necessary, a sufficiently low-magnetic metallic tubeand preferably coated with an electrically insulating oxide layer.

Furthermore, the coil carrier, which is designed as a small metallictube, preferably has a surface roughness of less than 5 μm. In this way,it is possible to reliably prevent the thin insulation of the coppercoil wire in the innermost winding layer of the coil from beingpunctured or contacted with little resistance.

Preferably, a sufficiently low-magnetic or non-magnetic metallic alloyis used as the material for the coil carrier, as the functioning of theWiegand wire is based on the fact that its hard magnetic shell is notcapable of switching the polarity of its soft magnetic core alone, butonly with the help of an externally applied magnetic field (see alsoliterature “Eigenschaften des Wiegand-Sensors”, messen+prüfen/automatik,May 1984). However, the sufficiently weak magnetic properties of theretaining and guiding element described here do not have a negativeimpact, provided that the functioning of the Wiegand wire is notimpaired. This is the case, for example, with soft magnetic materialsthat have a permeability coefficient of less than 50. This means thatthe concept according to the invention can also be implemented for theretaining and guiding element using low-magnetic alloys (see alsoliterature “Wissenswertes über Metall: Katalog der Firma Feldmann,Metall- und Schmiedekunst GmbH” or “Kleine Werkstoffkunde: FirmaBNK-Stahl und Edelstahl, Material AISI 303”), i.e. those with a lowcoercive force and/or remanence above zero.

According to a particularly preferred embodiment of the invention, thecoil carrier, i.e. the tube that surrounds the Wiegand wire section andholds the coil, is made of a nickel-titanium alloy. Such a thin tubeadvantageously proves to be extremely dimensionally stable. Besides itsfunction as a guiding part for the pulse or Wiegand wire and as thecarrier for the coil, it can also be connected to two separate plasticcoil body parts. As explained below, this connection can be carried outby pressing in the tube (force-fitting). However, it can also be carriedout by means of injection (form-fitting) or subsequent gluing. These twocoil body parts both then serve as partition elements for the coilwinding itself and also as carriers and fastening elements for theassembly and later connection of the module, e.g. on a circuit board.This provides particular advantages, especially in terms ofcost-effective production, as relatively expensive self-bonding wire canbe omitted and a normal enameled copper wire can be wound directly onthe tube and secured and contacted with the coil body parts.

According to a further aspect of the present invention, theabove-mentioned object according to the invention is also achieved bymeans of a method to produce a Wiegand module, in which a coil body, theinnermost winding of which defines an inner coil in which a Wiegand wiresection is enclosed, is formed in the course of a winding step. Thiswinding step is carried out by winding a winding wire material, which isintended to form the coil body, onto a metallic tube to form theintegral part of the Wiegand module. The metallic tube is preferablycoated with an electrically insulating oxide layer in the course of apreparatory process step.

BRIEF DESCRIPTION OF THE FIGURES

Further details and features of the invention are provided by thefollowing description in conjunction with the drawing. The figures showthe following:

FIG. 1 A schematic diagram to illustrate the structure of a Wiegandmodule according to the invention;

FIG. 2 An axial section view to illustrate the internal structure of theWiegand module according to FIG. 1;

FIG. 3 A perspective view of another variant of a Wiegand moduleaccording to the invention.

The drawings are not to scale and the supply lines to the coil areomitted in FIG. 2 for the sake of clarity. For the same reason, the gapbetween the pulse or Wiegand wire and the tube is shown greatlyenlarged.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 illustrates the structure of a Wiegand module 1 according to theinvention in the form of a perspective view. As shown in both FIGS. 1and 2, the Wiegand module 1 has two, preferably identically designed,coil holder parts 2 made of plastic, which are joined by pressing in thetubular retaining and guiding element 3 to form a force-fit connection.

The wire ends 5 of the multi-layer enameled copper wire coil 4 that iswound directly onto the retaining and guiding element are each clampedinto a slot on the underside of the coil holder parts 2, and the varnishis removed here to prepare for contacting on a circuit board. As analternative to this clamping, other methods to fix the wire ends arealso conceivable, e.g. ultrasonic welding. The corresponding surfaces 8of the plastic elements 2 can, and should, also be suitably metalizedfor improved soldering on the circuit board. For more precisepositioning of the whole module 1 on the circuit board, the coil holderparts 2 can be additionally fitted with suitable plastic tabs or pins 7.

Should it be necessary, for magnetic reasons, to magnetically stabilizethe ends of the Wiegand or pulse wire using ferrite beads 9, theseelements can be inserted or even injected into the plastic body. As aresult of the flexible design of the plastic elements, many forms thatare adapted to a specific application can generally be conceived,without affecting the inventive concept.

The pulse or Wiegand wire 6 is located inside the retaining and guidingelement. Adhesive can be used to prevent it from falling out (e.g. witha drop of silicone adhesive 10 at each end, as shown). At the same time,the adhesive seals the inside of the tube to keep out dirt and liquids.A permanently flexible adhesive ensures, with sufficient reliability,that no forces that impair the functioning of the pulse or Wiegand wirecan be exerted. However, if the expansion coefficient of the pulse orWiegand wires is virtually identical to that of the metallic tubes,direct welding is also possible at one or even both of the ends.

Wherever this kind of Wiegand module is to be used, it provides a simpleand inexpensive element for automatic assembly. The differentvariations, which may be necessary depending on the application, withdiffering numbers of windings, pulse or Wiegand wire lengths and formsof fastening element can be advantageously implemented on anapplication-specific basis by means of the simple and cost-savingadaptation of individual parts, such as the length or diameter of thetube.

FIG. 3 depicts a third variant of a Wiegand module 1 according to theinvention. The explanations of FIGS. 1 and 2 shall apply mutatismutandis. The contact and positioning pin 11 is passed through therespective coil holder part 2 and this pin 11 is contacted with therespective wire end 5 on one of the sides of the coil holder part 2facing away from the surface of the circuit board, as indicated.

LIST OF REFERENCE NUMBERS

-   -   1. Complete module structure    -   2. Coil holder part    -   3. Retaining and guiding element    -   4. Enameled copper wire coil    -   5. Wire end of the enameled copper wire coil    -   6. Pulse or Wiegand wire    -   7. Tab or pin for positioning    -   8. Contact surface for soldering procedure    -   9. Ferrite bead    -   10. Adhesive (e.g. silicon)

1. Wiegand wire arrangement, comprising: a Wiegand wire section; awinding device, the inner winding of which defines an inner coil; and aretaining and guiding element, which surrounds the Wiegand wire sectionand is enclosed in the inner coil, whereby the retaining and guidingelement consists of a non-magnetic or sufficiently low-magnetic metaland encloses the Wiegand wire section in the form of a tube.
 2. Wiegandwire arrangement according to claim 1, wherein the retaining and guidingelement includes an inner wall coated with an electrically insulatingoxide layer.
 3. Wiegand wire arrangement according to claim 1, whereinthe retaining and guiding element includes an outer wall coated with anelectrically insulating oxide layer.
 4. Wiegand wire arrangementaccording to claim 1, wherein the retaining and guiding element isformed of consists of a nickel-titanium alloy.
 5. Wiegand wirearrangement of claim 4, wherein the alloy consists of 50% nickel and 50%titanium.
 6. Wiegand wire arrangement of claim 1, wherein the retainingand guiding element has a surface roughness of below 5 μm.
 7. Wiegandwire arrangement of claim 1, wherein the retaining and guiding elementconnects the coil body parts.
 8. Wiegand wire arrangement according toclaim 7, wherein the coil body parts are joined in a force-fittingmanner.
 9. Wiegand wire arrangement according to claim 7, wherein thecoil body parts are joined in a form-fitting manner.
 10. A method toproduce a Wiegand module, in which a coil body, the innermost winding ofwhich defines an inner coil in which a Wiegand wire section is enclosed,is formed in the course of a winding step wherein the winding step iscarried out by winding a winding wire material, which is intended toform the coil body, onto a metallic tube to form the integral part ofthe Wiegand module.
 11. The method claim 10, characterized in that themetallic tube is coated with an electrically insulating oxide layer inthe course of a preceding process step.